Reconfigurable Doherty amplifier for efficient amplification of signals with variable PAPR

This paper proposes a reconfigurable Doherty amplifier capable of efficiently amplifying signals with variable peak-to-average power ratios (PAPR). A small number of electronically tunable devices are used to preserve appropriate Doherty load modulation as the input signal PAPR varies. A reconfigurable Doherty amplifier demonstrator was designed and fabricated, using gallium nitride transistors, to operate at 2.6 GHz and to efficiently amplify signals with PAPR of 6, 9 and 12 dB. Continuous wave measurements revealed power added efficiencies of higher than 64% at 6 and 9 dB and 59% at 12 dB output back-off. A Volterra based digital predistortion technique was also applied to examine the linearizability of the demonstrator and an Adjacent Channel Power Ratio (ACPR) of better than 46 dBc was achieved using 20MHz excitation signals with different PAPR values.